Many different waste heat recovery systems from hot flue gas have been developed for high temperature furnaces. They include regenerators and recuperators to preheat oxidant for combustion such as air and oxygen, waste heat boilers to generate steam, preheaters for solid feed materials to the furnace, and thermo-chemical recuperators and regenerators to heat and reform fuel. In a glass melting furnace fired with fuel and oxygen a single waste heat recovery system such as oxygen heating regenerators as described in U.S. Pat. No. 5,921,771 can recover only a portion of the waste heat available in the hot flue gas. By combining two or more different heat recovery systems in parallel or in series more waste heat from hot flue gas can be recovered. For example a waste heat boiler can be installed in the downstream of a primary high temperature heat recovery system to generate steam and to cool down the flue gas. Another example is to combine oxygen heating regenerators and a thermochemical recuperator or thermochemical regenerators.
U.S. Pat. No. 6,113,874 discloses thermo-chemical heat recovery methods useful with furnaces employing regenerators wherein a stream of combustion products formed in the furnace is passed through a first regenerator to heat the first regenerator and cool the combustion products, and then a portion of the cooled combustion products is combined with fuel to form a mixture which is passed through a second heated regenerator wherein the mixture undergoes an endothermic reaction to form syngas that then passes into the furnace and is combusted.
The present invention comprises an improvement in this heat recovery method by combining a batch or cullet preheating system in the downstream, particularly useful in glass manufacture.